JP7358973B2 - Split nut opening/closing device - Google Patents

Description

The present invention relates to a split nut opening/closing device used in mold clamping devices such as injection molding machines and die casting machines.

Injection molding machines and die casting machines are equipped with a mold clamping device that applies mold clamping force to a fixed mold and a movable mold. With a clamping force applied between a pair of molds by a mold clamping device, molten resin is injected into an injection molding machine, and molten metal is press-fitted into a die casting machine. The mold clamping force is applied via a tie bar installed between the fixed mold and the movable mold, and this mold clamping force is applied by a pair of engaging screws formed on the outer peripheral surface of the tie bar and a pair of movable mold plates. It is transmitted by meshing split nuts made of split nut pieces. Regarding a split nut opening/closing device, for example, Patent Document 1 proposes a mechanism that opens and closes a pair of split nuts at the same time on the left and right or top and bottom for the purpose of shortening the opening/closing time and reducing costs.

Here, as disclosed in Patent Document 2, the tie bars constituting the mold clamping device have a cantilevered structure, so they may bend and hang downward due to their own weight. The free end of the tie bar is the position where the maximum amount of deflection occurs in the cantilever state, and this free end is eccentric downward with respect to the support center position of the tie bar. By the way, when clamping the mold, mold clamping force is applied to the tie bar, so the center axis of the tie bar moves along the line connecting the shortest distance between the fixed mold platen and the movable mold platen, so the center position of the free end of the tie bar is the center of the supporting end. overlaps with the position. At this time, the split nut must grip the tie bar during mold clamping, so generally the center position of the split nut is concentric with the support center position of the tie bar, that is, it meshes with a straight tie bar along the horizontal direction without drooping. It is set up like this. Therefore, when the support strength of the tie bar support portion loosens due to aging or the like and the tie bar becomes more deflected, the tie bar and the split nut come into contact with each other at the lower part of the free end of the tie bar when the split nut closes. At this time, the contact point between the tie bar and the split nut serves as a fulcrum, and a rotational moment is generated in the split nut piece by the closing force of the split nut. The closing force of the split nut is based on the thrust of the ball screw, but if an unacceptable load is generated between the screw shaft and the nut that make up the ball screw due to the rotational moment generated in the split nut piece, the ball screw may be damaged. There is.

Japanese Patent Application Publication No. 2011-11379 JP2018-99717A

As described above, an object of the present invention is to provide an opening/closing device that can reduce the rotational moment generated in the split nuts when applied to a mold clamping device including a mechanism that opens and closes a pair of split nuts simultaneously.

The split nut opening/closing device of the present invention has a first A split nut piece and a first B split nut piece, the first split nut grips a first tie bar, and a second A split nut piece and a second B split nut piece. and a second split nut that grips the second tie bar.
Further, the split nut opening/closing device of the present invention includes an opening/closing mechanism that opens and closes the first split nut and the second split nut. This opening/closing mechanism moves the first A-split nut piece and the second A-split nut piece together, and also moves the first B-split nut piece and the second B-split nut piece together.
This opening/closing mechanism applies an output from the drive source to one of the first B split nut piece and the second A split nut piece via a load point. The load point in this opening/closing mechanism is located below the center of the first split nut and the second split nut in the vertical direction.

In the split nut opening/closing device of the present invention, preferably, the load point is disposed forward of the center of the first split nut and the second split nut in the horizontal direction. This load point definition can replace the load point definition described above.

The split nut opening/closing device of the present invention preferably includes a first connecting rod that connects the first B split nut piece and the second B split nut piece, and a second connecting rod that connects the first A split nut piece and the second A split nut piece. A connecting rod.
In the split nut opening/closing device of the present invention, preferably, the first connecting rod is located below the first A rod in the vertical direction and rearward of the first A rod in the horizontal direction. and a first B rod. The second connecting rod includes a second A-rod and a second B-rod that is located below the second A-rod in the vertical direction and further forward in the horizontal direction than the second A-rod.

Preferably, in the split nut opening/closing device of the present invention, assuming that the longitudinal dimension of the first split nut and the second split nut is L, the second A rod and the first B rod are It is arranged within a range of 3/4×L from the front end.

The opening/closing mechanism in the present invention preferably includes a ball screw that opens and closes the first split nut and the second split nut.
This ball screw includes a screw shaft provided with a first threaded portion and a second threaded portion threaded in the opposite direction to the first threaded portion, a first ball nut fitted into the first threaded portion, and a second threaded portion threaded in the opposite direction to the first threaded portion. and a second ball nut fitted into the second threaded portion.
In this opening/closing mechanism, the output of the drive source is applied to the load point via the screw shaft, and the opening/closing operation of the first B split nut piece and the second B split nut piece is performed by the forward and backward movement of the first ball nut. The opening and closing operations of the first A-split nut piece and the second A-split nut piece are performed by the movement of the two ball nuts back and forth.

According to the present invention, the load point in the opening/closing mechanism is arranged below the center of the first split nut and the second split nut in the vertical direction. Therefore, according to the present invention, the fulcrum caused by contact between the hanging tie bar and the split nut can be brought closer to the load point caused by the drive source, so the rotational moment generated in the split nut can be reduced. As a result, according to the present invention, bending of the ball screw shaft can be suppressed, and damage caused by bending the screw shaft and galling of the sliding portion between the screw shaft and the nut can be prevented.

1 is a partially sectional side view showing a schematic configuration of a mold clamping device according to a first embodiment of the present invention. FIG. 1 is a front view showing a schematic configuration of a mold clamping device according to a first embodiment. The split nut opening/closing device according to the first embodiment is shown in an open state, in which (a) is a partially sectional front view, (b) is a partially sectional bottom view, and (c) is a side view. The split nut opening/closing device in a closed state according to the first embodiment is shown, in which (a) is a partially sectional front view and (b) is a partially sectional bottom view. The split nut opening/closing device according to the second embodiment is shown in an open state, with (a) being a partially sectional front view and (b) being a partially sectional bottom view. The split nut opening/closing device according to the third embodiment is shown in an open state, with (a) being a partially sectional front view and (b) being a partially sectional bottom view. FIG. 3 is a diagram for explaining the effect of the split nut opening/closing device according to the present embodiment, ((a) is a partially sectional front view, (b) is a partially sectional bottom view, and (c) is a side view.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
[First embodiment]
As shown in FIGS. 1 and 2, the mold clamping device 1 according to the first embodiment is movable forward and backward with respect to a base 10, a fixed mold platen 11 fixed to the base 10, and a fixed mold platen 11. A movable mold board 12 provided on a base 10 is provided. The mold clamping device 1 also includes tie bars 15A, 15B, 15C, and 15D provided across the fixed mold platen 11 and the movable mold platen 12, a movable mold platen moving means 18 that moves the movable mold platen 12 forward and backward, and a mold clamping device 18 that moves the movable mold platen 12 forward and backward. The split nut opening/closing device 20 is engaged with the tie bars 15A, 15B, 15C, and 15D when the split nut opening/closing device 20 is engaged with the tie bars 15A, 15B, 15C, and 15D.
In the mold clamping device 1, it is assumed that a vertical direction V and a horizontal direction H are defined as shown in FIGS. 1, 2, etc. Furthermore, in the mold clamping device 1 and the split nut opening/closing device 20, although not shown, the side on which the movable mold platen 12 is provided is defined as the front, and the side on which the fixed mold platen 11 is provided is defined as the rear. The definitions before and after this are relative.

[Fixed mold board 11, movable mold board 12]
The fixed mold board 11 is provided on one end side of the base 10 in the horizontal direction H, and the movable mold board 12 is provided so as to be slidable with respect to the base 10 and facing the fixed mold board 11. In addition, in the fixed mold platen 11 and the movable mold platen 12, the surfaces facing each other are referred to as front surfaces 11A and 12A, and the surfaces facing the front surfaces 11A and 12A are referred to as back surfaces 11B and 12B.

The fixed mold platen 11 can hold a fixed mold 13 on its front surface 11A, and the movable mold plate 12 can hold a movable mold 14 on its front surface 12A. A cavity is formed inside each of the fixed mold 13 and the movable mold 14 to which the molten material is supplied. Illustration of the cavity is omitted. When the mold clamping device 1 is used in an injection molding machine, the molten material is made of molten resin, and when the mold clamping device 1 is used in a die casting device, the molten material is made of molten metal such as an aluminum alloy.

The fixed mold platen 11 and the movable mold platen 12 are connected by a plurality of tie bars, particularly four tie bars 15A, 15B, 15C, and 15D in this embodiment. The four tie bars 15A, 15B, 15C, and 15D are arranged at the four corners of the fixed mold board 11 and the movable mold board 12 when viewed from the front. A sliding material may be interposed between the tie bars 15A, 15B, 15C, 15D and the movable mold platen 12 to suppress friction between them.

[Tie bar 15A, 15B, 15C, 15D]
The tie bars 15A, 15B, 15C, and 15D are provided with a piston 16 for generating mold clamping force at the end on the fixed mold platen 11 side. Furthermore, ring-shaped meshing teeth 17 are formed on the tie bars 15A, 15B, 15C, and 15D at the end portions on the side of the movable mold platen 12 that extend in the circumferential direction. The meshing teeth 17 mesh with meshing teeth formed on the inner peripheries of the first split nut 21 and the second split nut 22. Thereby, the tie bars 15A, 15B, 15C, and 15D are locked to the movable mold board 12. Note that some of the meshing teeth provided on the inner periphery of the first split nut 21 (second split nut 22) are omitted from illustration.
Furthermore, the base 10 is provided with, for example, an electric or hydraulic movable mold platen moving means 18, so that the movable mold platen 12 can be moved back and forth with respect to the fixed mold platen 11. FIG. 1 shows a mold closed state in which the movable mold platen 12 is moved toward the fixed mold platen 11 by the movable mold platen moving means 18, and the movable mold 14 is brought into contact with the fixed mold plate 13.

[Split nut opening/closing device 20]
Next, the split nut opening/closing device 20 will be explained with reference to FIGS. 2 and 3.
The split nut opening/closing device 20 of the mold clamping device 1 receives the load of the contact point (fulcrum) SP of the tie bars 15A, 15B, 15C, 15D and the first split nut 21, and the closing force (ball screw thrust) of the first split nut 21. By making the point FP close to the point FP, the rotational moment generated in the first split nut 21 can be reduced. As a result, according to the split nut opening/closing device 20, bending of the screw shaft 38 can be minimized, and damage due to bending of the screw shaft 38 and galling of the sliding portion between the screw shaft 38 and the first split nut 21 can be prevented. I can do it.

The mold clamping device 1 includes two split nut opening/closing devices 20. As shown in FIG. 2, one split nut opening/closing device 20 is related to the two tie bars 15A, 15B on the upper side of the vertical direction V, and the other split nut opening/closing device 20 is related to the two tie bars 15A, 15B on the lower side of the vertical direction V. This is related to tie bars 15C and 15D.

As shown in FIGS. 2 and 3, the split nut opening/closing device 20 includes, for example, a pair of first split nuts 21 and second split nuts 22 on the left and right, and a first connecting rod 25 and a second connecting rod 26. . The split nut opening/closing device 20 has two tie bars 15A, 15B on the upper side and two tie bars on the lower side among the four tie bars 15A, 15B, 15C, 15D on the back side 12B of the movable mold board 12. Corresponding to the tie bars 15C and 15D, they are provided in upper and lower two stages. Although the split nut opening/closing device 20 related to the two tie bars 15A, 15B arranged on the upper side will be described below, the split nut opening/closing device 20 arranged on the lower side also has a similar configuration.

As shown in FIGS. 3(a) and 3(b), the first connecting rod 25 includes two first rods 25A, 25B, and the second connecting rod 26 includes two second rods 26A, 26B. . The first rods 25A and 25B each slidably pass through the split nut piece 22A and connect the split nut piece 21B and the split nut piece 22B. The second rods 26A and 26B each slidably pass through the split nut piece 21B and connect the split nut piece 21A and the split nut piece 22A. As shown in FIG. 3(c), the first rod 25A and the first rod 25B are arranged in point-symmetrical positions, and the second rod 26A and the second rod 26B are also arranged in point-symmetrical positions. Thereby, the first rods 25A, 25B and the second rods 26A, 26B are arranged at the vertices of the rectangle. This arrangement is only an example of the present invention, and other arrangements may be used, for example, the first rod 25A and the first rod 25B may be arranged in the vertical direction V, and the second rod 26A and the second rod 26B may be arranged in the vertical direction V. good.

The two second rods 26A and 26B that connect the split nut pieces 21A and 22A together move the split nut pieces 21A and 22A back and forth. Further, the two first rods 25A and 25B that connect the split nut pieces 21B and 22B move the split nut pieces 21B and 22B back and forth in cooperation with each other.

[Drive source 30]
As shown in FIGS. 2 and 3, a drive source 30 for the split nut pieces 21A, 21B, 22A, and 22B is provided on the rear surface 12B of the movable mold platen 12 between the split nut pieces 21B and 22A. is provided. The drive source 30, which is an element of the split nut opening/closing device 20, is composed of a rotary electric motor capable of forward and reverse rotation, such as a servo motor. The drive source 30 is fixed to, for example, a bracket (not shown).
The drive source 30 reciprocates the split nut piece 21A of the first split nut 21 and the split nut piece 22A of the second split nut 22 in the horizontal direction H via a screw shaft 38 connected to an output shaft (not shown). In addition to this, the split nut piece 21B of the first split nut 21 and the split nut piece 22B of the second split nut 22 are reciprocated in the horizontal direction H. The reciprocating movement is performed between the first split nut 21 and the second split nut 22.

[Split nut opening/closing device 20]
As shown in FIG. 3, the split nut opening/closing device 20 includes a ball screw 37 that opens and closes the first split nut 21 and the second split nut 22 by the rotational driving force of the drive source 30.
The ball screw 37 includes a screw shaft 38, a first ball nut 39A that meshes with the screw shaft 38, and a second ball nut 39B that meshes with the screw shaft 38. The threaded shaft 38 has a first threaded portion 38A having a spiral shape around an area where the first ball nut 39A is engaged, and a second threaded threaded portion 38B which has a spiral shape around an area where the second ball nut 39B is engaged. , is provided. The first threaded portion 38A and the second threaded portion 38B have opposite threading directions, that is, winding directions.
The ball screw 37 has a plurality of rotations between the first threaded portion 38A of the screw shaft 38 and the first ball nut 39A, and between the second threaded portion 38B of the screw shaft 38 and the second ball nut 39B. A ball acts as a moving object.

The split nut opening/closing device 20 includes a connecting body 34 that connects the second rod 26A and the second rod 26B. The connecting body 34 has one end fixed to the second rod 26A and the other end fixed to the second rod 26B. Further, the connecting body 34 is fixed to a second ball nut 39B between one end side and the other end side. Therefore, the second rod 26A and the second rod 26B reciprocate in the horizontal direction H as the second ball nut 39B of the ball screw 37 reciprocates.

The first ball nut 39A has its tip fixed to the split nut piece 21B. Therefore, when the screw shaft 38 rotates clockwise, for example, the split nut piece 21B is pushed by the first ball nut 39A and moves to one side in the horizontal direction H. Since the split nut piece 21B and the split nut piece 22B are connected by the first rods 25A and 25B, the split nut piece 22B moves to one side in the horizontal direction H as the split nut piece 21B moves.

The second ball nut 39B is fixed to the connecting body 34. Therefore, when the screw shaft 38 rotates clockwise, for example, the split nut piece 22A is pushed by the second ball nut 39B and moves to the other side in the horizontal direction H. Since the split nut piece 22A and the split nut piece 21A are connected by the second rods 26A and 26B, the split nut piece 21A moves to the other side in the horizontal direction H as the split nut piece 22A moves.
The first threaded portion 38A and the first ball nut 39A, and the second threaded portion 38B and the second ball nut 39B have the same specifications such as the thread lead and outer diameter, except for the direction of thread cutting.

[Operation of split nut opening/closing device 20]
Next, the operation of the split nut opening/closing device 20 will be described with reference to FIGS. 3 and 4.
The split nut opening/closing device 20 has an open position where the first split nut 21 and the second split nut 22 open the corresponding tie bars 15A, 15B, and an open position where the first split nut 21 and the second split nut 22 open the corresponding tie bars 15A, 15B. , 15C, and 15D. FIG. 3 shows the split nut opening/closing device 20 in the open position, and FIG. 4 shows the split nut opening/closing device 20 in the closed position. For example, in the case of injection molding, the movement from the open position to the closed position is performed prior to the clamping of the movable mold 14 and the fixed mold 13 by the piston 16, which is a prerequisite for injection molding. Furthermore, in the case of injection molding, for example, the movement from the closed position to the open position is performed after filling a predetermined amount of molten resin into the cavity between the movable mold 14 and the fixed mold 13. This is performed prior to opening the fixed mold 13.

[Movement from open position to closed position]
To move from the open position to the closed position, power is supplied to the drive source 30 to rotate its output shaft. Note that the direction of rotation of the output shaft when moving from the open position to the closed position is defined as the forward direction.

When the output shaft of the drive source 30 is rotated in the forward direction, the ball screw shaft 38 connected to the output shaft is rotated in the forward direction. At this time, since the threading directions of the first ball nut 39A and the second ball nut 39B are opposite to each other, the rotation of the shared ball screw shaft 38 causes the first ball nut 39A to be cut on one L side in the horizontal direction H ( 3(a)), and the second ball nut 39B moves to the other R side in the horizontal direction H (right side in FIG. 3(a)). As a result, the split nut piece 21A and the split nut piece 22A move to one R side in the horizontal direction H, and the split nut piece 21B and the split nut piece 22B move to the other L side in the horizontal direction H. As shown in FIG. 4, the split nut pieces 21A and 21B grip the tie bars 15A, 15B, 15C, and 15D, and the split nut pieces 22A and 22B grip the tie bars 15A, 15B, 15C, and 15D. When it moves to the predetermined position to be gripped, the power supply to the drive source 30 is stopped, and the rotational drive of the output shaft is stopped. This completes the operation of the split nut pieces 21A, 21B, 22A, and 22B from the open state to the closed state by the split nut opening/closing device 20, and mold clamping is ready.

[Movement from closed position to open position]
To move from the closed position to the open position, in the state shown in FIG. 4, power is supplied to the drive source 30 to rotate the output shaft in the opposite direction. Then, the ball screw shaft 38 connected to the output shaft rotates in the opposite direction. Thereby, the split nut piece 21A and the split nut piece 22A move toward the other L side, and the split nut piece 21B and the split nut piece 22B move toward the one R side. As shown in FIG. 3, when the split nut piece 21A and the split nut piece 21B are separated from the tie bar 15A by a predetermined distance, and when the split nut piece 22A and the split nut piece 22B are separated from the tie bar 15B by a predetermined distance, the driving source The power supply to 30 is stopped, and the rotational drive of the output shaft is stopped. This completes the operation of the split nut pieces 21A, 21B, 22A, and 22B from the closed state to the open state by the split nut opening/closing device 20, and preparations for mold opening and mold release are completed.

[Effects produced by the split nut opening/closing device 20]
Next, the effects of the split nut opening/closing device 20 will be explained in the following order: factors for obtaining the effects, a configuration for achieving the effects, and the effects.

[Factors requiring effectiveness]
There are two reasons for this. The first factor is that the tie bars 15A, 15B in the split nut opening/closing device 20 have a cantilever structure. The second factor is that a mechanism is provided to open and close the first split nut 21 and the second split nut 22 arranged in the horizontal direction H as a pair.
Regarding the first factor, the cantilever structure, as shown in FIG. , the end on the side gripped by the first split nut 21 and the second split nut 22 is a free end. Therefore, the tie bars 15A, 15B are deflected downward in the vertical direction V at their free ends, and are eccentrically downward relative to the supporting ends.

Next, regarding the second factor, the mechanism that opens and closes the first split nut 21 and the second split nut 22 arranged in the horizontal direction H as a pair, the split nut pieces 21A and 21B that make up the first split nut 21 are as follows. The split nut pieces 22A and 22B constituting the second split nut 22 open and close in the horizontal direction H. Therefore, when the first split nut 21 and the second split nut 22 are in the open state, as shown in FIG. The tie bar 15B is in contact with the split nut pieces 22A, 22B. These contact points are called contact points SP. In addition, in FIGS. 7A and 7B, straight arrows in the horizontal direction H consisting of solid lines and dashed-dotted lines represent loads applied to each member.

As shown in FIG. 7(a), there is a distance LV2 in the vertical direction V between the contact point SP of the tie bar 15A and the split nut pieces 21A and 21B and the load point FP to which the thrust of the ball screw 37 is applied. A rotational moment MV in the vertical direction V is generated in the split nut pieces 21A, 21B with the contact point SP as a fulcrum (SP). Bending occurs in the screw shaft 38 according to the rotational moment MV. That is, when the rotational moment MV is generated, the split nut pieces 21A and 21B tilt, and the first ball nut 39A fixed to the split nut piece 21B also tilts in accordance with the split nut piece 21B. The screw shaft 38 and the first ball nut 39A are fitted precisely, and the tilt that occurs in the first ball nut 39A is transmitted to the screw shaft 38 because there is insufficient clearance between it and the screw shaft 38 to absorb it. I end up getting beaten up. This generates bending stress on the screw shaft 38, but if this bending stress is large, the screw shaft 38 may be damaged or galling may occur between the screw shaft 38 and the first ball nut 39A and the second ball nut 39B. .

As shown in FIG. 7(b), also in the horizontal direction H, a rotational moment MH in the horizontal direction H with the abutment point SP as the fulcrum (SP) is generated in the split nut pieces 21A, 21B, so the screw shaft 38 Bending will occur.

As described above, rotational moments MV and MH can occur in both the vertical direction V and the horizontal direction H, but the first embodiment proposes a means for dealing with the rotational moment MV in the vertical direction V, and the second embodiment proposes a means for dealing with the rotational moment MV in the vertical direction V. A means for dealing with the rotational moment MH in the horizontal direction H is proposed.

[Arrangement of ball screw 37 in vertical direction V]
Corresponding to the rotational moment MV in the vertical direction V, the split nut opening/closing device 20 specifies the position of the ball screw 37 in the vertical direction V. In other words, as shown in FIGS. 3 and 4, the load point FP from the ball screw 37 via the first ball nut 39A is vertically lower than the center CV of the first split nut 21 and the second split nut 22 in the vertical direction V. It is arranged below the direction V. The axis C38V of the screw shaft 38 passes through the load point FP. By arranging the load point FP in this manner, the distance LV1 between the contact point (fulcrum) SP and the load point FP can be made shorter than the distance LV2 in FIG. 7 .

[effect]
As described above, since the split nut opening/closing device 20 can shorten the distance LV1 from the fulcrum SP to the load point FP, the rotational moment MV can be kept small. On the other hand, as shown in FIG. 7(a), when the vertical center CV of the first split nut 21 and the second split nut 22 coincides with the load point FP, the distance from the fulcrum SP to the load point FP is Distance LV2 is greater than distance LV1. Therefore, according to this embodiment, since the rotational moment MV in the vertical direction V can be suppressed, the bending stress generated in the ball screw 37 can also be suppressed to a small level. Moreover, according to the present embodiment, the bending stress can be reduced by specifying the position of the ball screw 37 without adding a new member, so that the cost does not increase.

[Second embodiment]
Next, a second embodiment according to the present invention will be described with reference to FIG. 5. The second embodiment will be explained focusing on the differences from the first embodiment, and the same elements as the first embodiment will be given the same reference numerals in the drawings and explained. Omitted.

In the split nut opening/closing device 120 according to the second embodiment, as particularly shown in FIG. 5(b), the ball screw 37 is arranged close to the free ends FE of the tie bars 15A, 15B in the horizontal direction H. That is, in the horizontal direction H, the split nut opening/closing device 120 has a load point FP from the ball screw 37 via the first ball nut 39A, which is lower than the center CH of the first split nut 21 and the second split nut 22 in the vertical direction V. is placed in front in the horizontal direction H. The axis C38H of the screw shaft 38 passes through the load point FP. By arranging the load point FP in this manner, the distance LH1 between the contact point (fulcrum) SP and the load point FP can be made shorter than the distance LH2 in FIG. 7 .

According to the split nut opening/closing device 120 of the second embodiment configured as described above, since the rotational moment MH in the horizontal direction H can be suppressed, the bending stress generated in the ball screw 37 can also be suppressed to a small level.

[Third embodiment]
Next, a third embodiment according to the present invention will be described with reference to FIG. 6. The third embodiment will be described with a focus on differences from the first and second embodiments, and the same elements as those in the first and second embodiments will be designated by the same reference numerals in the drawings. The explanation will be omitted.

As described below, the split nut opening/closing device 220 according to the third embodiment has a configuration that combines the first embodiment and the second embodiment, and also has a configuration that further suppresses the rotational moment MH in the horizontal direction H. Equipped with
First, as shown in FIG. 6(a), the ball screw 37 has a distance from the ball screw 37 via the first ball nut 39A that is lower than the center CV of the first split nut 21 and the second split nut 22 in the vertical direction V. The load point FP is arranged below the vertical direction V. This configuration corresponds to the first embodiment.

In addition, as shown in FIG. 6(b), the split nut opening/closing device 220 is arranged so that the center CH of the first split nut 21 and the second split nut 22 in the vertical direction V is more A load point FP from the ball screw 37 via the ball screw 37 is located forward in the horizontal direction H. This configuration corresponds to the second embodiment.

Further, as shown in FIG. 6(b), the split nut opening/closing device 220 moves the second rod 26A and the first rod 25B, and the center CH of the first split nut 21 and the second split nut 22 in the horizontal direction H. It is shifted forward from a position symmetrical to the second rod 26A and the first rod 25B with respect to the reference. By doing so, the second rod 26A and the first rod 25B approach the center CH, so that the distance LH1B between the load point FP and the fulcrum SP by the first connecting rod 26A and the first rod 25B can be shortened.

Here, as shown in FIG. 6(b), the longitudinal dimension of the first split nut 21 and the second split nut 22 is LN. Then, the second A rod 26A and the first B rod 25B are preferably arranged within a range of 3/4×LN from the front end FF of the first split nut 21 and the second split nut 22. More preferably, the second A rod 26A and the first B rod 25B are arranged within a range of 1/2×LN from the front end FF of the first split nut 21 and the second split nut 22.

As described above, according to the split nut opening/closing device 220, the rotational moment MV in the vertical direction V and the rotational moment MH in the horizontal direction H can be reduced. Therefore, according to the third embodiment, the bending stress generated in the screw shaft 38 can be made smaller than that in the first and second embodiments, which prevents damage to the screw shaft 38 and the first ball nut 39A. The occurrence of galling with the two-ball nut 39B can be more effectively suppressed.

Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments.
For example, in the embodiment described above, by using the ball screw 37 including the first threaded portion 38A and the second threaded portion 38B that are threaded in opposite directions, the split nut piece 21A and the split nut piece 21B are connected to each other. A split nut opening/closing mechanism that moves the split nut piece 21B and the split nut piece 22B in opposite directions in the horizontal direction H is illustrated. However, the present invention is not limited to opening and closing a split nut using a ball screw 37 that includes a first threaded portion 38A and a second threaded portion 38B that are threaded in opposite directions. For example, it can be applied to a split nut opening/closing structure that opens and closes the first split nut 21 and the second split nut 22 using a pair of ball nuts, ball screw shafts, and link mechanisms disclosed in Patent Document 2. In addition, opening and closing of this split nut can be realized not only with the ball screw 37. For example, the mechanism disclosed in Patent Document 2 is applicable. As the driving source of the mechanism disclosed in Patent Document 2, a hydraulic cylinder can be used in addition to a rotary electric motor. Therefore, the drive source applied to the present invention is also not limited to a rotary electric motor. As described above, the present invention can be applied to a known split nut opening/closing mechanism.

1 Mold clamping device 10 Base 11 Fixed mold board 12 Movable mold board 13 Fixed mold 14 Movable mold 15A, 15B, 15C, 15D Tie bar 20, 120, 220 Split nut opening/closing device 21, 22 Split nut 21A, 21B, 22A , 22B Split nut piece 25 First connecting rod 25A, 25B First rod 26 Connecting rod 26A, 26B Second rod 30 Drive source 34 Connecting body 38 Threaded shaft 38A First threaded part 38B Second threaded part 39A First ball nut 39B 2nd ball nut V Vertical direction H Horizontal direction CH Horizontal center CV Vertical center FE Free end SP Fulcrum, contact point FP Load point MH Rotating moment MV Rotating moment

Claims (7)

A first split nut that has a first A split nut piece and a first B split nut piece and grips the first tie bar, and a second split nut that has a second A split nut piece and a second B split nut piece and grips the second tie bar. split nut and
Responsible for opening and closing operations of the first split nut and the second split nut, and causes the first A split nut piece and the second A split nut piece to reciprocate in the horizontal direction in cooperation with each other, and the first B split nut piece and the second split nut piece An opening/closing mechanism for reciprocating the second B split nut pieces in the horizontal direction in cooperation with each other,
The opening/closing mechanism is
Applying a horizontal output from a drive source to one of the first B split nut piece and the second A split nut piece via a load point, and
The load point is located below the vertical center of the first split nut and the second split nut,
A split nut opening/closing device characterized by:
The load point is located forward of the horizontal center of the first split nut and the second split nut,
The split nut opening/closing device according to claim 1.
a first connecting rod that connects the first B split nut piece and the second B split nut piece;
a second connecting rod connecting the first A-split nut piece and the second A-split nut piece;
The split nut opening/closing device according to claim 1 or 2.
The first connecting rod is
a first A-rod, and a first B-rod located below the first A-rod in the vertical direction and rearward of the first A-rod in the horizontal direction;
The second connecting rod is
a second A-rod, and a second B-rod arranged below the second A-rod in the vertical direction and in front of the second A-rod in the horizontal direction;
The split nut opening/closing device according to claim 3.
If the longitudinal dimension of the first split nut and the second split nut is LN,
The second A rod and the first B rod are
disposed within a range of 3/4×LN from the front ends of the first split nut and the second split nut,
The split nut opening/closing device according to claim 4.
The opening/closing mechanism is
comprising a ball screw responsible for opening and closing operations of the first split nut and the second split nut,
The ball screw is
a screw shaft provided with a first threaded portion and a second threaded portion threaded in the opposite direction to the first threaded portion;
comprising a first ball nut fitted to the first threaded part and a second ball nut fitted to the second threaded part,
An output from the drive source is applied to the load point via the screw shaft, and opening and closing operations of the first B split nut piece and the second B split nut piece are performed by the forward and backward movement of the first ball nut, and , the opening and closing operations of the first A-split nut piece and the second A-split nut piece are performed by the forward and backward movement of the second ball nut;
The split nut opening/closing device according to any one of claims 3 to 5.
A first split nut that has a first A split nut piece and a first B split nut piece and grips the first tie bar, and a second split nut that has a second A split nut piece and a second B split nut piece and grips the second tie bar. split nut and
Responsible for the opening and closing operations of the first split nut and the second split nut, moves the first A split nut piece and the second A split nut piece in cooperation, and the first B split nut piece and the second B split nut piece. Equipped with an opening/closing mechanism that moves the pieces together,
The opening/closing mechanism is
The first split nut and the second split nut are opened and closed in the direction of the output shaft of the drive source,
Applying an output from the drive source to one of the first B split nut piece and the second A split nut piece via a load point, and
The load point is located forward of the horizontal center of the first split nut and the second split nut,
A split nut opening/closing device characterized by:

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